The presence of a cardiac pacemaker (PM) is currently considered an absolute contraindication to MR imaging, and most patients with PM are excluded from having MRI. In 2002 there were approximately 2.4 million patients in the US with cardiac PM, and this number is growing by 80,000 annually. A previous study has shown that MRI is indicated in 17% of all patients with pacemakers within 12 months of device placement 1, demonstrating the need for a practical and safe approach for performing MRI on PM patients.

The aim of this study is to develop a strategy for safe performance of MR imaging at 1.5T, which included exclusion of pacemaker dependent patients and those requiring imaging of the thorax, restriction of specific absorption rate (SAR) values to minimize the risk of lead heating, and PM reprogramming to avoid interference from time varying gradient fields. The safety of this approach is then evaluated in a large group of PM patients including assessment of potential myocardial thermal injury by measuring serum troponin I and pacing capture thresholds, and performing a 3-month follow-up to evaluate long-term effects.

Eligibility

Genders Eligible for Study:

Both

Accepts Healthy Volunteers:

No

Criteria

Inclusion Criteria:

Urgent need for an MRI examination

Presence of a Medtronic PM system manufactured between 1993 and 2004

Stable pacemaker physical parameters

Battery voltage > 2.7 V

Battery impedance < 2000 Ohm

Battery estimated remaining lifetime > 6 months

Lead impedances 200-2000 Ohm

Stable pacing parameters

Pacing capture threshold <2.5V at a pulse duration of 0.4ms

Sensing > 5mV

Minimum 3 months since pacemaker and lead implantation

Exclusion Criteria:

PM system manufacturer other than Medtronic

History of ventricular tachycardia (VT) or ventricular fibrillation

Unstable angina

Myocardial infarction within the previous 3 months

Cardiothoracic surgery within the previous 3 months

Complete atrioventricular block

Absolute pacemaker dependence

Heart rate < 40 bpm or

Heart rate < 60 bpm producing neurological symptoms

Presence of an abdominal pacemaker with lead length > 70 cm

Presence of MRI incompatible bioimplants or other MRI incompatible materials

Request for an MR examination of the chest, including the heart, breasts and thoracic spine

Contacts and Locations

Choosing to participate in a study is an important personal decision. Talk with your doctor and family members or friends about deciding to join a study.
To learn more about this study, you or your doctor may contact the study research staff using the Contacts provided below.
For general information, see Learn About Clinical Studies.

Please refer to this study by its ClinicalTrials.gov identifier: NCT00336011